Directory UMM :Data Elmu:jurnal:A:Applied Soil Ecology:Vol12.Issue2.Apr1999:
Applied Soil Ecology 12 (1999) 129±137
Species abundance of earthworms in arable and pasture
soils in south-eastern Australia
P.M. Melea, M.R. Carterb,*
a
Institute for Integrated Agricultural Development, R.M.B. 1145, Chiltern Valley Road, Rutherglen, Vic., Australia
b
Agriculture and Agri-Food Canada, Research Centre, Charlottetown, PEI, Canada CIA 7M8
Received 15 November 1997; accepted 10 December 1998
Abstract
Earthworms play an important role in soil ecology and can serve as practical indicators in land quality evaluation. The
abundance and distribution of earthworms were determined in 84 cropping and pasture soils in north-east Victoria and
southern New South Wales (NSW), Australia. Overall, an average density of 89 earthworms mÿ2 was found, with an average
species richness of 1±2 per site, indicating relatively low abundance and species poverty. Introduced lumbricid earthworms,
Aporrectodea trapezoides and A. caliginosa were the most widely distributed (88% and 61% of all sites, respectively) and
numerically dominant (respective population densities of 35.8 and 32.1 mÿ2). Soils under pasture supported on average 3.2
times more earthworms than those under cropping. The age structure of populations varied with species, introduced lumbricids
and acanthodrilids displayed an adult-dominant structure and the native megascolecids displayed a juvenile-dominant
population. Indigenous earthworms belonged to a single genus, Spenceriella. Whilst not occurring in high densities these
indigenous earthworms were widespread in their distribution and their numbers were negatively correlated with soil P, K, and
Mg suggesting an adaptation to low levels of soil fertility. Although the relationship between earthworm densities and mean
annual total precipitation (MATP) was not close (r2 0.35), of the 33 sites containing >100 earthworms mÿ2, 25 received
MATP in excess of 600 mm. Correlations between earthworm densities and a range of physical and chemical parameters were
generally poor. This may highlight the short-comings of these parameters in describing distribution patterns. # 1999 Elsevier
Science B.V. All rights reserved.
Keywords: Earthworm distribution; Exotic and native earthworm species; Arable; Pasture; Soil properties; Spenceriella
1. Introduction
Earthworms can signi®cantly improve the fertility
and plant productivity of dryland agricultural soils in
Australia. Superior in®ltration and bioporosity in
cropping (Tisdall, 1985; Carter et al., 1994) and
orchard soils (Tisdall, 1978) have been related to
*Corresponding author. Tel.: +1-902-566-6869; fax: +1-902566-6821; e-mail: carterm@em.agr.ca
greater earthworm abundance. Accelerated amelioration of acid soils through lime burial (Baker et al.,
1993a) and reductions in the severity of both take-all
(Stephens et al., 1994a) and bare-patch (Stephens et
al., 1994b) diseases of wheat have been all attributed
to the activity of earthworms. Some research has also
de®ned agricultural factors affecting activity such as
grazing (Lobry de Bruyn and Mele, 1993) and tillage
(Rovira et al., 1987; Carter et al., 1994; Mele and
Carter, 1999), and climatic factors related to rainfall
0929-1393/99/$ ± see front matter # 1999 Elsevier Science B.V. All rights reserved.
PII: S 0 9 2 9 - 1 3 9 3 ( 9 9 ) 0 0 0 0 6 - 2
130
P.M. Mele, M.R. Carter / Applied Soil Ecology 12 (1999) 129±137
distribution (Baker, 1997; Lobry de Bruyn and Kingston, 1997).
Some earthworm species have been implicated
more strongly in soil improvement than others. This
has been largely attributed to variation in the ecological functions of individual species (Lee, 1985). The
recent focus on earthworms as practical indicators of
sustainable agricultural management (Lobry de
Bruyn, 1997), has highlighted basic knowledge gaps
in terms of what earthworms are and what physical,
chemical and agricultural management factors in¯uence their distribution and abundance. Knowledge on
the ecological appropriateness of species encountered
will aid in the selection of species to supplement
existing populations.
Although several surveys exist in Australia that
determine the species distribution of earthworms in
agricultural and urban land (Mele et al., 1993), very
few have attempted to quantify species abundance.
Baker et al. (1992) attempted to relate species abundance to a suite of soil physical and chemical parameters, while other studies have attempted to relate
dominant earthworm species to a range of soil and
agronomic conditions (Bucker®eld et al., 1997) or to
aspects of soil structural stability (Ketterings et al.,
1997). In order to quantify the impact of earthworms
in arable agricultural land and to investigate the
potential for manipulation of earthworm fauna, the
factors that effect species distribution and abundance
must be de®ned and quanti®ed.
The purpose of this study was to characterise earthworm fauna in both cropping and pasture soils in
north-eastern Victoria and southern New South Wales
(NSW). The speci®c objectives of the study were to: (1)
determine the abundance and distribution of earthworms, (2) assess earthwormage structure, and (3)relate
overall and species abundance of earthworms to a range
of standard soil physical and chemical parameters.
2. Materials and methods
A survey of the earthworm fauna in 84 cropping and
pasture soils in north-eastern Victoria and southern
NSW (Fig. 1) was undertaken in 1990 during the cool
wet season (August±October) when species tend to
concentrate in the surface soil. This is the period of
peak earthworm activity (Baker et al., 1992, 1993b).
Fig. 1. Location of earthworm survey sites in south-eastern
Australia.
The survey area, which comprised approximately
200 km2, is generally characterised by a modi®ed
mediterranean climate with wet, frosty winters (mean
annual total precipitation 300±1000 mm) and hot dry
summers with extended periods of summer drought.
The soil morphology was dominately duplex, with
texture contrasts between the A and B horizons (Stace
et al., 1968).
The passive earthworm sampling procedure of
Baker et al. (1992) was adopted. At each site, two
parallel transect lines, each approximately 50 m long
and 10 m apart were measured so that samples could
be taken every 10 m with a total of 10 sampling points.
At each sampling point, a block of soil (0.1 m2 by
0.1 m) was removed and the soil ®nely hand-sifted to
collect all earthworm lifestages including cocoons.
Specimens from each block were placed into individual containers of 70% ethanol for preservation pending identi®cation.
Prior to microscopic identi®cation, all specimens
were rinsed in water, placed in fresh 70% ethanol and
identi®ed using a WILD M3C1 dissecting microscope (magni®ed 10±40 times) with an endoscopic
light source (Intralux 5000, Volpi1). Introduced species were classi®ed according to Sims and Gerard
(1985) and indigenous species to the level of genus
using Jamieson (1974) where applicable. Lifestages
were separated as adults (clitellate), subadults (nonclitellate, sexual pores present), juveniles (non-clitellate, sexual pores absent) and cocoons. Fresh weight
(biomass) was determined for each lifestage and for
overall population at each site.
P.M. Mele, M.R. Carter / Applied Soil Ecology 12 (1999) 129±137
A composite soil sample from each sampling point
was also collected at each site. Soil was dried (408C,
24 h) and either ground (2 mm, and organic C
and total N, 0.25 mm) or sieved (1±2 mm), for physical analyses. Soil organic C was measured by an
improved chromic acid digestion and spectrophotometric procedure (Heanes, 1984), while total N was
determined by dry combustion using a LECO CNS
analyser. Soil available K (i.e., Skene K) and P (i.e.,
NaHCO3, Olsen P) were determined according to the
respective methods of Skene (1956) and Olsen and
Sommers (1982). Soil pH was determined using both
0.01 M CaCl2 and distilled water. Exchangeable
cations (Ca, Mg, Na, and K) were extracted with
1 M NH4OAc (1 : 10, soil : extractant) and the cations
determined by ICP-AES analysis (Rayment and Higginson, 1992). Soil particle size distribution was
determined for clay (%), sand (%, >500 mm, 250±
500 mm and 0.5 mm, oven dried aggregates
were sieved (0.5 mm sieve) in 0.5 M NaOH, redried
(1058C, 24 h), and calculated as above. Gravimetric
water (wt.%), average annual precipitation and where
possible, crop and pasture history data were also
collected.
Multiple regression step-down analyses were
employed on earthworm population density values to
derive parsimonious equations of signi®cant relationships with soil chemical and physical variables (Genstat
5, 1987). A multiple regression analysis was also performed on mean annual total precipitation and earthworm density data sets using precipitation values taken
from MetAccess1 Analysing Weather records (Bureau
of Meteorology and CSIRO; Horizon Technology Pty
Ltd). Table CurveTM was used to derive a correlation
coef®cient (Jandel Scienti®c, copyright 1991).
131
3. Results
3.1. Earthworm species and abundance
Earthworm fauna in north-eastern Victoria and
southern NSW contained at least 10 species belonging
to three families (Table 1). Six of these species were
introduced Lumbricidae and three were introduced
Acanthrodrilids. A single indigenous genus, Spenceriella, was also identi®ed with a further six different
morphs categorised (G. Dyne, personal communication, 1991). The total average species abundance (all
sites combined) varied widely from densities of
35.8 mÿ2 for Aporrectodea caliginosa to A. trapezoides > Spenceriella spp. >
A. rosea > M. phosphoreus > M. dubius > Lumbricus
rubellus. Both A. caliginosa and A. trapezoides were
more abundant in pasture than cropping soils, being
4.8 and 3.9 times greater, respectively in pasture sites.
Spenceriella species were 6.7 times more abundant in
pasture soils than in cropping soils whilst other lumbricids, A. rosea and L. rubellus were only slightly
more abundant in pasture soils. In contrast, the acanthrodrilids, M. dubius and M. phosphoreus were 2 and
1.1 times more abundant, respectively, in cropping
soils than in pasture soils.
3.2. Earthworm age structure
At the time of sampling, the age structure of the
earthworm population varied widely between species
(Fig. 2). The two most abundant species, A. caliginosa
and A. trapezoides showed similar age structures with
132
P.M. Mele, M.R. Carter / Applied Soil Ecology 12 (1999) 129±137
Table 1
Earthworm population densities (number mÿ2) in crop and pasture soils of north-east Victoria and south NSW
Species
Crop
Sites
a
Pasture
Average all sites
Mean SE
Max.
Sites
Mean SE
Max.
Mean SE
Lumbricidae
Aporrectodea caliginosa
A. trapezoides
A. tuberculata
A. rosea
Octolasion cyaneum
Lumbricus rubellus
13
29
2
8
2
3
11.5 6.9
12.5 3.5
Species abundance of earthworms in arable and pasture
soils in south-eastern Australia
P.M. Melea, M.R. Carterb,*
a
Institute for Integrated Agricultural Development, R.M.B. 1145, Chiltern Valley Road, Rutherglen, Vic., Australia
b
Agriculture and Agri-Food Canada, Research Centre, Charlottetown, PEI, Canada CIA 7M8
Received 15 November 1997; accepted 10 December 1998
Abstract
Earthworms play an important role in soil ecology and can serve as practical indicators in land quality evaluation. The
abundance and distribution of earthworms were determined in 84 cropping and pasture soils in north-east Victoria and
southern New South Wales (NSW), Australia. Overall, an average density of 89 earthworms mÿ2 was found, with an average
species richness of 1±2 per site, indicating relatively low abundance and species poverty. Introduced lumbricid earthworms,
Aporrectodea trapezoides and A. caliginosa were the most widely distributed (88% and 61% of all sites, respectively) and
numerically dominant (respective population densities of 35.8 and 32.1 mÿ2). Soils under pasture supported on average 3.2
times more earthworms than those under cropping. The age structure of populations varied with species, introduced lumbricids
and acanthodrilids displayed an adult-dominant structure and the native megascolecids displayed a juvenile-dominant
population. Indigenous earthworms belonged to a single genus, Spenceriella. Whilst not occurring in high densities these
indigenous earthworms were widespread in their distribution and their numbers were negatively correlated with soil P, K, and
Mg suggesting an adaptation to low levels of soil fertility. Although the relationship between earthworm densities and mean
annual total precipitation (MATP) was not close (r2 0.35), of the 33 sites containing >100 earthworms mÿ2, 25 received
MATP in excess of 600 mm. Correlations between earthworm densities and a range of physical and chemical parameters were
generally poor. This may highlight the short-comings of these parameters in describing distribution patterns. # 1999 Elsevier
Science B.V. All rights reserved.
Keywords: Earthworm distribution; Exotic and native earthworm species; Arable; Pasture; Soil properties; Spenceriella
1. Introduction
Earthworms can signi®cantly improve the fertility
and plant productivity of dryland agricultural soils in
Australia. Superior in®ltration and bioporosity in
cropping (Tisdall, 1985; Carter et al., 1994) and
orchard soils (Tisdall, 1978) have been related to
*Corresponding author. Tel.: +1-902-566-6869; fax: +1-902566-6821; e-mail: carterm@em.agr.ca
greater earthworm abundance. Accelerated amelioration of acid soils through lime burial (Baker et al.,
1993a) and reductions in the severity of both take-all
(Stephens et al., 1994a) and bare-patch (Stephens et
al., 1994b) diseases of wheat have been all attributed
to the activity of earthworms. Some research has also
de®ned agricultural factors affecting activity such as
grazing (Lobry de Bruyn and Mele, 1993) and tillage
(Rovira et al., 1987; Carter et al., 1994; Mele and
Carter, 1999), and climatic factors related to rainfall
0929-1393/99/$ ± see front matter # 1999 Elsevier Science B.V. All rights reserved.
PII: S 0 9 2 9 - 1 3 9 3 ( 9 9 ) 0 0 0 0 6 - 2
130
P.M. Mele, M.R. Carter / Applied Soil Ecology 12 (1999) 129±137
distribution (Baker, 1997; Lobry de Bruyn and Kingston, 1997).
Some earthworm species have been implicated
more strongly in soil improvement than others. This
has been largely attributed to variation in the ecological functions of individual species (Lee, 1985). The
recent focus on earthworms as practical indicators of
sustainable agricultural management (Lobry de
Bruyn, 1997), has highlighted basic knowledge gaps
in terms of what earthworms are and what physical,
chemical and agricultural management factors in¯uence their distribution and abundance. Knowledge on
the ecological appropriateness of species encountered
will aid in the selection of species to supplement
existing populations.
Although several surveys exist in Australia that
determine the species distribution of earthworms in
agricultural and urban land (Mele et al., 1993), very
few have attempted to quantify species abundance.
Baker et al. (1992) attempted to relate species abundance to a suite of soil physical and chemical parameters, while other studies have attempted to relate
dominant earthworm species to a range of soil and
agronomic conditions (Bucker®eld et al., 1997) or to
aspects of soil structural stability (Ketterings et al.,
1997). In order to quantify the impact of earthworms
in arable agricultural land and to investigate the
potential for manipulation of earthworm fauna, the
factors that effect species distribution and abundance
must be de®ned and quanti®ed.
The purpose of this study was to characterise earthworm fauna in both cropping and pasture soils in
north-eastern Victoria and southern New South Wales
(NSW). The speci®c objectives of the study were to: (1)
determine the abundance and distribution of earthworms, (2) assess earthwormage structure, and (3)relate
overall and species abundance of earthworms to a range
of standard soil physical and chemical parameters.
2. Materials and methods
A survey of the earthworm fauna in 84 cropping and
pasture soils in north-eastern Victoria and southern
NSW (Fig. 1) was undertaken in 1990 during the cool
wet season (August±October) when species tend to
concentrate in the surface soil. This is the period of
peak earthworm activity (Baker et al., 1992, 1993b).
Fig. 1. Location of earthworm survey sites in south-eastern
Australia.
The survey area, which comprised approximately
200 km2, is generally characterised by a modi®ed
mediterranean climate with wet, frosty winters (mean
annual total precipitation 300±1000 mm) and hot dry
summers with extended periods of summer drought.
The soil morphology was dominately duplex, with
texture contrasts between the A and B horizons (Stace
et al., 1968).
The passive earthworm sampling procedure of
Baker et al. (1992) was adopted. At each site, two
parallel transect lines, each approximately 50 m long
and 10 m apart were measured so that samples could
be taken every 10 m with a total of 10 sampling points.
At each sampling point, a block of soil (0.1 m2 by
0.1 m) was removed and the soil ®nely hand-sifted to
collect all earthworm lifestages including cocoons.
Specimens from each block were placed into individual containers of 70% ethanol for preservation pending identi®cation.
Prior to microscopic identi®cation, all specimens
were rinsed in water, placed in fresh 70% ethanol and
identi®ed using a WILD M3C1 dissecting microscope (magni®ed 10±40 times) with an endoscopic
light source (Intralux 5000, Volpi1). Introduced species were classi®ed according to Sims and Gerard
(1985) and indigenous species to the level of genus
using Jamieson (1974) where applicable. Lifestages
were separated as adults (clitellate), subadults (nonclitellate, sexual pores present), juveniles (non-clitellate, sexual pores absent) and cocoons. Fresh weight
(biomass) was determined for each lifestage and for
overall population at each site.
P.M. Mele, M.R. Carter / Applied Soil Ecology 12 (1999) 129±137
A composite soil sample from each sampling point
was also collected at each site. Soil was dried (408C,
24 h) and either ground (2 mm, and organic C
and total N, 0.25 mm) or sieved (1±2 mm), for physical analyses. Soil organic C was measured by an
improved chromic acid digestion and spectrophotometric procedure (Heanes, 1984), while total N was
determined by dry combustion using a LECO CNS
analyser. Soil available K (i.e., Skene K) and P (i.e.,
NaHCO3, Olsen P) were determined according to the
respective methods of Skene (1956) and Olsen and
Sommers (1982). Soil pH was determined using both
0.01 M CaCl2 and distilled water. Exchangeable
cations (Ca, Mg, Na, and K) were extracted with
1 M NH4OAc (1 : 10, soil : extractant) and the cations
determined by ICP-AES analysis (Rayment and Higginson, 1992). Soil particle size distribution was
determined for clay (%), sand (%, >500 mm, 250±
500 mm and 0.5 mm, oven dried aggregates
were sieved (0.5 mm sieve) in 0.5 M NaOH, redried
(1058C, 24 h), and calculated as above. Gravimetric
water (wt.%), average annual precipitation and where
possible, crop and pasture history data were also
collected.
Multiple regression step-down analyses were
employed on earthworm population density values to
derive parsimonious equations of signi®cant relationships with soil chemical and physical variables (Genstat
5, 1987). A multiple regression analysis was also performed on mean annual total precipitation and earthworm density data sets using precipitation values taken
from MetAccess1 Analysing Weather records (Bureau
of Meteorology and CSIRO; Horizon Technology Pty
Ltd). Table CurveTM was used to derive a correlation
coef®cient (Jandel Scienti®c, copyright 1991).
131
3. Results
3.1. Earthworm species and abundance
Earthworm fauna in north-eastern Victoria and
southern NSW contained at least 10 species belonging
to three families (Table 1). Six of these species were
introduced Lumbricidae and three were introduced
Acanthrodrilids. A single indigenous genus, Spenceriella, was also identi®ed with a further six different
morphs categorised (G. Dyne, personal communication, 1991). The total average species abundance (all
sites combined) varied widely from densities of
35.8 mÿ2 for Aporrectodea caliginosa to A. trapezoides > Spenceriella spp. >
A. rosea > M. phosphoreus > M. dubius > Lumbricus
rubellus. Both A. caliginosa and A. trapezoides were
more abundant in pasture than cropping soils, being
4.8 and 3.9 times greater, respectively in pasture sites.
Spenceriella species were 6.7 times more abundant in
pasture soils than in cropping soils whilst other lumbricids, A. rosea and L. rubellus were only slightly
more abundant in pasture soils. In contrast, the acanthrodrilids, M. dubius and M. phosphoreus were 2 and
1.1 times more abundant, respectively, in cropping
soils than in pasture soils.
3.2. Earthworm age structure
At the time of sampling, the age structure of the
earthworm population varied widely between species
(Fig. 2). The two most abundant species, A. caliginosa
and A. trapezoides showed similar age structures with
132
P.M. Mele, M.R. Carter / Applied Soil Ecology 12 (1999) 129±137
Table 1
Earthworm population densities (number mÿ2) in crop and pasture soils of north-east Victoria and south NSW
Species
Crop
Sites
a
Pasture
Average all sites
Mean SE
Max.
Sites
Mean SE
Max.
Mean SE
Lumbricidae
Aporrectodea caliginosa
A. trapezoides
A. tuberculata
A. rosea
Octolasion cyaneum
Lumbricus rubellus
13
29
2
8
2
3
11.5 6.9
12.5 3.5